using System;

public class RecFib
{
    static void Main()
    {
        int value = Int16.Parse(Console.ReadLine());

        Console.WriteLine((int)rFib(value));
    }

    public static long rFib(int n)
    {
        if(n == 0 || n == 1)
        {
            return n;
        }
        return rFib(n - 2) + rFib(n - 1);
    }
}
